1. Field of the Invention
The present invention relates to a reinforcing frame structure for a tractor for use in coupling a front loader to the front of the tractor and a rear working implement such as a backhoe to the rear of the tractor. More particularly, the invention relates to a reinforcing frame structure detachably attached to a body of an agricultural tractor or the like to reinforce rigidity thereof and to couple working implements to the front and rear of the tractor body.
2. Description of the Related Art
Japanese Patent Publication Kokai No. 6-32188, for example, discloses such a reinforcing frame structure. This reinforcing frame structure is dividable transversely of a tractor body to couple a front loader to the front of the tractor body, and a different working implement to the rear of the tractor body. This reinforcing frame structure includes triangular plates fixed to pipe-like right and left frames to support a rear axle case. The rear axle case has ends thereof extending through the triangular frames for support. Therefore, the reinforcing frame structure must be assembled sideways to the tractor body before attaching the rear wheels.
U.S. Pat. No. 5,248,237 discloses another example of such reinforcing frame structure. This structure may have a working implement such as a front loader and a rear working implement such as a backhoe coupled thereto. The reinforcing frame structure includes two reinforcing frames arranged on each side of a tractor body. A first reinforcing frame extending laterally of the tractor body and a second reinforcing frame extending slightly inside the first reinforcing frame are both fixedly connected at forward ends thereof to a cross bar extending transversely of the tractor body.
GB 22 18 891 discloses a further example of reinforcing frame structure, in which a front loader is coupled to the front of a tractor, and a backhoe to the rear thereof. Reinforcing frames are arranged on right and left sides of a tractor body. These reinforcing frames are connected to the tractor body through two brackets. The reinforcing frames include mast mounts formed in forward end positions thereof for receiving masts of the front loader.
Further, U.S. Pat. No. 4,737,067 discloses a mounting mechanism (not referred to as a reinforcing frame) for attaching a working implement to a tractor. This patent discloses a pair of frames as one example, which are spaced from each other by a distance smaller than a width of a tractor body. These frames are attached in forward positions thereof to a transmission case through brackets or directly to an engine.
The first three prior publications have a common feature that right and left frames are connected to the tractor body independently of each other. With the reinforcing frame structure disclosed in each of these publications, each of the reinforcing frames is connected sideways to the tractor body or to varied elements or brackets attached to the tractor body. The reinforcing frame structure cannot be attached in assembled state to a completed tractor body. Thus, as far as the efficiency of assembling the reinforcing frame structure to a completed tractor body is concerned, the above structures disclosed in the prior publications including the fourth publication leave considerable room for improvement. With the reinforcing frame structure connected to the tractor body, a force may be applied to right and left couplings of the front loader, and a force and moment may occur to a rear working implement coupling due to an operation of the backhoe. None of these publications describe or specifically disclose a measure for diminishing the magnitude of such a force (stress) and moment conducted through the reinforcing frame structure to the tractor body.
In U.S. Pat. No. 5,248,237, for example, tubular elements extending laterally of the tractor body include mast mounts for receiving masts of the front loader. These mast mounts are formed in the tubular elements (or cross bars) extending transversely of the tractor body. As seen from FIGS. 2 and 3 of this patent, the cross bars extending transversely are connected to the tractor body through brackets, respectively. Forces applied to the right and left masts of the front loader are conducted to the tractor body through the mast mounts, tubular elements and brackets. Consequently, the stress or moment is considered to act in reduced magnitude on the tractor body. However, since the cross bars do not extend over an entire width of the tractor body, a large part of strain energy due to the stress or moment applied to the mast mounts must in substance be absorbed by lateral walls of the tractor body.
In the structure disclosed in Japanese Patent Publication Kokai No. 6-32188, a backhoe acting as the rear working implement is coupled to a pair of triangular plates formed in rearward positions of the reinforcing frames. The forces applied to right and left couplings of the backhoe are transmitted through the right and left triangular plates to right and left extensions of the rear axle case. Thus, a large part of the forces (stress or moment) produced at the backhoe couplings due to the force conducted from the backhoe is conducted directly to the rear axle case.
In the structure disclosed in GB 22 18 891, masts are attached directly to forward ends of the reinforcing frames extending laterally of the tractor body. The reinforcing frames are connected adjacent rear ends thereof to the tractor body through two brackets. Thus, components of force and moment resulting from an operation of the front loader are conducted to the tractor body through the right and left reinforcing frames and brackets.